Message Passing Interface

The Message Passing Interface (MPI) is a computer communications protocol. It is a de facto standard for communication among the nodes running a parallel program on a distributed memory system. MPI implementations consist of a library of routines that can be called from Fortran, C, C++ and Ada programs. The advantage of MPI over older message passing libraries is that it is both portable (because MPI has been implemented for almost every distributed memory architecture) and fast (because each implementation is optimized for the hardware on which it runs). Foundation for Microsoft Clustering Server. Often compared with PVM and at one stage merged with PVM to form PVMMPI.

Example program

Here is "Hello World" in MPI. Actually we send a "hello" message to each processor, manipulate it trivially, send the results back to the main processor, and print the messages out.

/*
 test of MPI
*/
#include <mpi.h>
#include <stdio.h>
#include <string.h>

int main(int argc, char *argv[])
{
  char idstr[32];
  char buff[128];
  int numprocs;
  int myid;
  int i;
  MPI_Status stat; 

  MPI_Init(&argc,&argv); 
  MPI_Comm_size(MPI_COMM_WORLD,&numprocs); 
  MPI_Comm_rank(MPI_COMM_WORLD,&myid); 

  if(myid == 0)
  {
    printf("We have %d processors\n", numprocs);
    for(i=1;i<numprocs;i++)
    {
      sprintf(buff, "Hello %d! ", i);
      MPI_Send(buff, 128, MPI_CHAR, i, 0, MPI_COMM_WORLD);
    }
    for(i=1;i<numprocs;i++)
    {
      MPI_Recv(buff, 128, MPI_CHAR, i, 0, MPI_COMM_WORLD, &stat);
      printf("%s\n", buff);
    }
  }
  else
  {
    MPI_Recv(buff, 128, MPI_CHAR, 0, 0, MPI_COMM_WORLD, &stat);
    sprintf(idstr, "Processor %d ", myid);
    strcat(buff, idstr);
    strcat(buff, "reporting for duty\n");
    MPI_Send(buff, 128, MPI_CHAR, 0, 0, MPI_COMM_WORLD);
  }

  MPI_Finalize();
  return 0;
}

External links

References

This article is based on material taken from the Free On-line Dictionary of Computing prior to 1 November 2008 and incorporated under the "relicensing" terms of the GFDL, version 1.3 or later.

Example program

See also

External links

References